12.1.1. Analysis Type Settings

The Analysis Type settings enable you to specify an analysis as being Steady State, Transient, or Transient Blade Row. Steady-state analyses are used to model flows that do not change over time; transient analyses model flows that are time-dependent. Transient blade row analyses are transient analyses that have special handling for turbomachinery cases.

The Analysis Type options are described in the following sections:

 

12.1.1.1. Steady State

No further settings are required for the Steady State option. Modeling advice for setting the time scale for steady-state simulations is provided in Steady-state Time Scale Control in the CFX-Solver Modeling Guide.

 

12.1.1.2. Transient

 
12.1.1.2.1. Time Duration

Set Option to determine the length of the transient analysis:

  • Total Time

  • Time per run

  • Maximum Number of Timesteps

  • Number of Timesteps per Run

  • Coupling Time Duration

For details, see Time Duration in the CFX-Solver Modeling Guide.

 
12.1.1.2.2. Time Steps

Set Option to determine the size of timesteps for the run:

  • Timesteps

  • Timesteps for the Run

  • Adaptive

  • Coupling Timesteps

The Timesteps and Timesteps for the Run parameters can accept a single value or lists. If a list is entered, it should be comma separated, for example, 2, 1.2, 2.4. If an expression is used, you must associate units with each item in the list, for example, 2 [s], 1.2 [s], 2.4 [s]. In addition, it is possible to define multiples of a timestep value in the user interface when not using the expression method. For example, you could enter 5*0.1, 2*0.5, 10*1 as a list of values, and set the units to [s] separately. The corresponding CCL that would be generated would be:

0.1 [s], 0.1 [s], 0.1 [s], 0.1 [s], 0.1 [s], 0.5 [s], 0.5 [s], 1 [s], 1 [s], 1 [s], 1 [s], 1 [s], 1 [s], 1 [s], 1 [s], 1 [s], 1 [s]

If you accidentally enter 5*0.1 [s], 2*0.5 [s], 10*1 [s] as an expression, the multiplication would be carried out, and the corresponding CCL that would be generated would be:

0.5 [s], 1.0 [s], 10.0 [s]

For details, see Transient Timestep Control in the CFX-Solver Modeling Guide.

When Adaptive time is selected, set one of the following three conditions for Timestep Adaption to automate the calculation of timestep size:

  • Number of Coefficient Loops

  • RMS Courant Number

  • MAX Courant Number

For details, see Transient Timestep Control in the CFX-Solver Modeling Guide.

 
12.1.1.2.3. Initial Time

Set the Option to specify the Initial Time for a transient analysis.

  • Automatic

  • Automatic with Value

  • Value

  • Coupling Initial Time

For details, see Initial Time in the CFX-Solver Modeling Guide.

 

12.1.1.3. Transient Blade Row

The Transient Blade Row option is required in order to access the Transient Blade Row models:

  • None

  • Profile Transformation

  • Time Transformation

  • Fourier Transformation

The Initial Time settings must be specified in the Analysis Type settings. For details on these settings, see Initial Time.

For instructions on setting up and using Transient Blade Row models, see Transient Blade Row Modeling in the CFX-Solver Modeling Guide.